High-voltage electrostatic generator

ABSTRACT

A high voltage is developed by conveying electrostatic charges to a high-voltage electrode, by means of an endless conveyor chain comprising conductive links alternating with insulating links. The conductive links comprise cylindrical pellets with cylindrical openings extending axially therein. The insulating links have enlarged spherically rounded end portions swingably received in the cylindrical openings. Pivot pins extend between the enlarged end portions and the cylindrical pellets. The conveyor is trained around wheels having spring contactors thereon for transferring charges to and from the pellets. Channel-shaped induction electrodes are positioned opposite the conveyor where it makes and breaks contact with the wheels. Operating voltages for some of the induction electrodes are obtained by idler pulleys contacting the conveyor. Each idler pulley preferably has one or more spring contactors thereon for engaging the pellets. Additional induction electrodes are preferably provided opposite the idler pulleys.

United States Patent Inventors Raymond G. Herb Madison; James A. Ferry,Middleton, both of Wis. Appl. No. 829,066 Filed May 29, 1969 PatentedOct. 12, 1971 Assignee National Electrostatics Corp. Middleton, Wis.

HIGH-VOLTAGE ELECTROSTATIC GENERATOR 24 Claims, 14 Drawing Figs.

US. Cl 310/6 .H02n l/00 Field of Search 310/5, 6, 7; 322/2.1; 339/9References Cited UNITED STATES PATENTS 2,697,793 12/1954 Trump et al.310/5 9/1962 Hand 310/6 ABSTRACT: A high voltage is developed byconveying electrostatic charges to a high-voltage electrode, by means ofan endless conveyor chain comprising conductive links alternating withinsulating links. The conductive links comprise cylindrical pellets withcylindrical openings extending axially therein. The insulating linkshave enlarged spherically rounded end portions swingably received in thecylindrical openings. Pivot pins extend between the enlarged endportions and the cylindrical pellets. The conveyor is trained aroundwheels having spring contactors thereon for transferring charges to andfrom the pellets. Channel-shaped induction electrodes are positionedopposite the conveyor where it makes and breaks contact with the wheels.Operating voltages for some of the induction electrodes are obtained byidler pulleys contacting the conveyor. Each idler pulley preferably hasone or more spring contactors thereon for engaging the pellets.Additional induction electrodes are preferably provided opposite theidler pulleys.

PATENTE-Dnm 12 I97! 3.612.919

' SHEET 1 HF 4 l 36 28 1 N VEN T 025 Paymond G. Herb PATENTEDUBT 12 Ian3,612,919

SHEET 2 0F 4 PATENTEUum 12 sen SHEET 3 OF 4 i l/////[ u i iillHIGH-VOLTAGE ELECTROSTATIC GENERATOR This invention relates tohigh-voltage electrostatic generators of the type in which an extremelyhigh voltage is produced by conveying electrostatic charges to ahigh-voltage electrode on which the charges are accumulated.

One object of the present invention is to provide a high-voltageelectrostatic generator having a new and improved charge carryingconveyor which has a high-charge-carrying capacity, is capable ofoperating at high speeds, and is invulnerable to damage due to possiblesparking or flashovers along the conveyor.

Thus, the present invention preferably utilizes an endless chargecarrying conveyor comprising a chain having electrically conductivelinks alternating with electrically insulating links. Pivot means areprovided between the links. The electrically conductive links arepreferably in the form of cylindrical pellets having axially disposedcylindrical openings therein. The electrically insulating links areswingably mounted within the cylindrical openings by means of pivotpins. Preferably, the electrically insulating links comprise enlargedspherically rounded end portions swingably received in the cylindricalopenings. The pellets are preferably made of metal while the insulatinglinks are made of nylon or other suitable plastic material. Theinsulating links may also be made of a ceramic material.

A further object is to provide a high-voltage electrostatic generatorhaving improved systems for transferring charges to and from thepellets, with maximum efficiency and virtually no sparking.

Thus, the invention preferably utilizes an endless conveyor havingconductive pellets with insulating elements therebetween. The conveyoris trained around main wheels having edge portions with grooves thereinfor receiving the conveyor. The edge portion of each wheel is preferablymade of nylon or other suitable plastic material to minimize noise andwear. The charges are transferred to and from the pellets by means ofcontactors on the wheels. The contactors project into the groove on eachwheel to engage the pellets. Preferably, the contactors are in the formof contact springs or other resiliently biased elements to providespring pressure between the contactors and the pellets.

Induction electrodes are preferably provided where the pellets make andbreak contact with the wheels. The operating voltages for at least someof the induction electrodes are provided by idler pulleys which contactthe pellets at points spaced from the main wheels. Each idler pulleypreferably has a rim portion made of nylon or other suitable plasticmaterial for quiet running and minimum wear. At least one resilientcontactor is preferably provided on each idler pulley to engage thepellets. Additional induction electrodes are preferably providedopposite the idler pulleys.

The induction electrodes substantially prevent sparking between thepellets and the pulleys and also betweenthe pellets and the main wheels.Thus, the erosion of the pellets due to sparking is virtuallyeliminated. The elimination of sparking also increases the maximumvoltage capacity of the generator.

Further objects, advantages and features of the present invention willappear fromthe following description, taken with the accompanyingdrawings, in which: v

FIG. 1 is a diagrammatic elevational section of a high voltageelectrostatic generator, to be described as an illustrative embodimentof the present invention.

FIG. 2 is a diagrammatic elevation of the charge-transporting system forthe generator.

FIG. 3 is a fragment elevational section corresponding to the lowerportion of FIG. 2 and showing additionaldetails of thecharge-transporting system.

FIG. 4 is a sectional plan view taken generally along the line 4-4 inFIG. 3.

FIG. 5 is an edge view of one of the main wheels shown in FIGS. 3 and 4.

FIG. 6 is an enlarged fragmentary section taken through the main wheelof FIG. 5.

FIG. 7 is a fragmentary elevation corresponding to the upper portion ofFIG. 2.

FIG. 8 is an elevational section taken line 8-8 in FIG. 7.

FIG. 9 is a top view of the assembly shown in FIG. 7.

FIG. 10 is an elevational section taken generally along the line l010 inFIG. 7.

FIG. 11 is a fragmentary enlarged sectional view corresponding to theleft-hand portion of FIG. 7.

FIG. 12 is a fragmentary enlarged section taken generally along the linel2-l2 in FIG. 11.

FIG. 13 is an enlarged elevational section of the endless pel let chainemployed in the high-voltage generator.

FIG. 14 is an enlarged elevational section of one of the conductivepellets.

As already indicated, FIG. 1 illustrates a high-voltage electrostaticgenerator 10 which will find many applications, but is especially welladapted to provide an extremely high voltage for accelerating chargedparticles in an evacuated accelerating tube 12, to carry out studies innuclear physics or to generate high-energy x-rays. The high-voltagegenerator 10 is preferably housed within a pressure tank or casing 14.In this way, the generator 10 may be surrounded by a high-pressureatmosphere, so as to provide greatly improved resistance to high-voltageflashovers. Accordingly, the high-voltage generator 10 may be operatedat a much higher voltage than would be possible in air at normalatmospheric pressure. While highpressure air may be employed within thetank I4, it is preferred to provide an atmosphere comprising a gashaving an extremely high dielectric strength such as sulfurhexafluoride, for example. The sulfur hexafluoride may be mixed withairbut the use of pure sulfur hexafluoride is preferred. Other known orsuitable gases may also be employed to increase the insulating value ofthe atmosphere around the highvoltage generator. The tank 14 is usuallymade of steel or other metal and is maintained at ground potential.

Within the tank 14, the high-voltage generator 10 comprises a groundedsupporting frame or member 16, mounted on one end of the tank 14. Ahigh-voltage electrode 18 is disposed in the tank 14 near the oppositeend thereof and is connected to the frame 16 by a plurality of insulatorassemblies 20. The high voltage electrode 18 is hollow and thus isformed with a chamber 22 therein. All of the surfaces of thehigh-voltage electrode 18 are smoothly curved and rounded to avoid anyundue concentration of the electric field around the high-voltageelectrode. The illustrated high-voltage electrode 18 has a cylindricalwall portion 24 which merges smoothly into a spherically curved endportion 26. The construction of the highvoltage electrode 18 is suchthat the possibility of sparking between the high-voltage electrode andthe tank 14 is minimized.

The high-voltage electrode I8 is capable of accumulating electricalcharges to an extremely high voltage. The insulator assemblies 20 arecapable of withstanding the high voltage. It will be seen thattheaccelerating tube 12 extends between the high-voltage electrode 18 andthe grounded tank 14.

A charge-transporting system 28 is provided to carry successiveelectrical charges to the high-voltage electrode 18. These charges areaccumulated on the high-voltage electrode 18 so that the voltage thereonbuilds up to an extremely high value.

It will be seen that the charge-transporting system 28 comprises one ormore endless conveyors 30, each of which is threaded around at least twomain wheels or pulleys 32 and 34. While a single endless conveyor couldbe employed, the illustrated machine utilizes two parallel conveyors, todouble the charge-carrying capacity of the charge-transporting system28, as will be seen from FIG. 4.

As shown in FIGS. 1 and 2, the first supporting wheel 32 for eachconveyor 30 is mounted on the grounded frame 16 while the second wheel34 is mounted within the high-voltage electrode 18. The wheel 32 issuitably driven, preferably by an electric motor 36.

The details of each endless conveyor 30 are shown to best advantage inFIGS. 13 and 14. The conveyor 30 comprises conductive elements 38alternating with electrically insulating generally along the elements40. The conductive elements 38 are preferably in the form of metalpellets, connected into an endless string by the insulating elements 40.As shown, the conductive elements or pellets 38 are circular in crosssection and are preferably of a generally cylindrical shape. The pellets38 have rounded ends to avoid any sharp edges which might cause a highconcentration of the electric field around the pellets. In this way, thepossibility of sparking along the pellets is minimized.

The illustrated pellets 38 have cylindrical openings 42, axiallydisposed therein. While the openings 42 are illustrated as extendingcompletely through the pellets, they could extend only part way intoeach end.

Each pellet 38 has a generally cylindrical exterior. How ever, toimprove the running of the pellets around the wheels 32 and 34, eachpellet 38 is preferably formed with a circumferential groove 44 aroundits midsection. The pellet 38 has cylindrical surfaces 46 at oppositesides of the groove 44.

The electrically insulating elements 40 may assume a variety of forms,as long as they provide flexible interconnections between the pellets38. However, the insulating elements 40 are preferably in the form oflinks made of plastic, ceramic or other insulating materials. Onepreferred plastic material is nylon, which provides the advantages ofhigh strength, low wear and self-lubrication, as well as good electricalinsulation.

Pivot elements 48 are preferably provided between the insulatingelements or links 40 and the conductive pellets 38 so that the elements38 and 40 form the alternate links of a continuous chain. Theillustrated pivot elements 48 are in the form of pins extending throughopenings 50 and 52 in the elements 38 and 40. The pins 50 are preferablypress fitted into place so that they are securely retained.

The insulating links 40 are preferably formed with enlarged sphericallyrounded end portions 54 which are swingable within the cylindricalopenings 42 in the pellets 38. Each of the illustrated links 40 has areduced midsection 56 between the enlarged end portions 54. The mainwheels or pulleys 32 and 34 may be essentially the same in construction.The details of the wheels are shown to best advantage in FIGS. 6 and I].It will be seen that each of the wheels 32 and 34 is formed with aperipheral groove 58 to receive and retain the pellets 38 of thecorresponding endless conveyor 30. The groove 58 is preferably roundedin cross section, to correspond with the cylindrical shape of thepellets 38.

To afford low noise and wear, each of the wheels 32 and 34 is preferablyprovided with a plastic peripheral rim portion 60, made of nylon orother suitable material. The peripheral groove 58 is formed in the rimportion 60. To secure the illustrated rim portion 60 to the wheel, theillustrated rim portion is formed with an inwardly projecting flange 62of reduced thickness, adapted to be clamped between metal plates 64 and66, forming the main body of the wheel. Another metal plate 68 isclamped between the inner portions of the plates 64 and 66.

While it is highly advantageous to employ a plastic material for the rimportion 60 of the wheel, the plastic material does not provide anelectrical connection between the pellets 38 and the metal parts 64, 66and 68 of the wheel. Such electrical connection is necessary to providefor electrical charge transfers, to and from the pellets. In the case ofthe wheel 32, charges are transferred by way of the wheel from thegrounded frame 16 to the pellets 38. In the case of the wheel 34,charges are transferred by way of the wheel from the pellets 38 to thehigh-voltage electrode 18.

To provide for such charge transfers, each of the wheels 34 and 36 isprovided with one or more contactors 70 which engage the pellets 38 andare connected electrically to the metal parts of the wheel. Theillustrated wheels are provided with a series of such contactors 70spaced around the periphery of each wheel. The contactors 70 preferablyproject into the peripheral groove 58 so as to engage the pellets 38.Moreover, the mounting of the contactors 70 is preferably resilient sothat they exert spring pressure against the pellets. The illustratedcontactors 70 are formed as the outer portions of U- shaped wire springs72 having their inner portions welded or otherwise secured to a metalband 74, extending around the periphery of the wheel. The metal band 74is connected electrically to the metal plates 64, 66 and 68 by suitablemeans, illustrated as comprising one or more spring arms 76 projectinginwardly from the band and engaging clamping screws 78 which extendthrough the plates 64 and 66. The curved guide groove 58 for the pellets38 is formed with a deeper central groove 80 to receive the band 74 andthe springs 72. It will be seen from FIG. 6 that the contactors 70,constituting the outer portions of the springs 72, extend outwardly fromthe groove 80, into the groove 58.

As shown to best advantage in FIG. 2, the charge-transporting system 28preferably comprises two induction electrodes 82 and 83, opposite themain wheel 32, and two more induction electrodes 84 and 85, opposite theother wheel 34. The induction electrodes 82-85 are located at the pointswhere the endless conveyor 30 makes and breaks contact with the wheels32 and 34.

The induction electrodes 82-85 are employed to charge and discharge thepellets 38 with a minimum of sparking. As shown, the induction electrode82 is maintained at a fairly high voltage by a direct-current powersupply 88. Typically, the power supply 88 delivers 10 to 50 kilovolts.The induction electrode 82 induces charges on the pellets 38 as theydepart from the wheel 32. The actual flow of the charges to the pelletsoccurs before the pellets part company from the wheel 32, so that thereis virtually no sparking between the pellets and the wheel.

The pellets 38 carry the charges to the second wheel 34, through whichthey are transferred to the high-voltage electrode 18. The inductionelectrode 85 is maintained at a fairly high voltage relative to thehigh-voltage electrode I8 so that the induction electrode 85 is able tobind the charges on the pellets 38 until after the pellets make contactwith the wheel 84. Thus, the induction electrode 85 prevents sparkingbetween the pellets and the wheel 34.

The induction electrode 84 is located opposite the wheel 34 at the pointwhere the return flight of the conveyor 30 parts company from the wheel.The induction electrode 84 is provided with a high voltage relative tothe high-voltage electrode 18 so that charges are induced on the pellets38 as they depart from the wheel 34 in their return flight to the wheel32. The charges induced on the returning pellets are of the oppositesign from the charges carried to the high-voltage electrode 18 by theincoming pellets. Thus, the polarity of the voltage on the inductionelectrode 84, relative to the high-voltage electrode 18, is opposite tothe polarity of the voltage on the induction electrode 85. For example,if the high-voltage electrode I8 is to be charged positively, thecharges on the incoming pellets will be positive, and the voltage on theinduction electrode 85 will be less positive than that on thehigh-voltage electrode. The voltage on the induction electrode 84 willbe more positive than that on the high-voltage electrode 18, so thatnegative charges will be carried away from the high-voltage electrode bythe returning pellets.

The charges on the returning pellets are discharged to ground throughthe wheel 32. The induction electrode 83 is located opposite the wheel32, where the returning pellets engage the wheel. This inductionelectrode is operated at a high voltage so as to bind the charges on thereturning pellets until they actually engage the wheel 32. In this way,sparking is prevented. The polarity of the voltage on the inductionelectrode 83 is opposite to that on the induction electrode 82.

When the main high-voltage electrode or dome I8 is to be positivelycharged, the voltage relationships will be as follows:

For negative charging of the high-voltage electrode 18, the signs of allvoltages will be reversed from those given in the above table.

In order to provide the operating voltages for the induction electrodes83, 84 and 85, it is preferred to employ idler pulleys 93, 94 and 95 toengage the conveyor 30 at points near the wheels 32 and 34. The pulley93 is connected to the induction electrode 83 and is positioned toengage the pellets 38 near the beginning of their outward flight betweenthe wheels 32 and 34. Thus, the charged pellets maintain the pulley 93and the induction electrode 83 in a charged condition. An additionalelectrode 103 is disposed so as to influence the pellets 38 as theyengage the pulley 93. The induction electrode 103 is grounded and thusis at zero voltage.

The pulley 94 is connected to the induction electrode 84 and ispositioned to engage the incoming pellets 38 shortly before they arriveat the wheel 34. Thus, the pulley 94 and the induction electrode 84 aremaintained in a charged condition by the pellets. If the pellets arepositively charged, the pulley 94 and the induction electrode 84 arecharged with a voltage which is more positive then that on thehigh-voltage electrode 18. Another induction electrode 104 is preferablypositioned so as to influence the pellets as they engage the pulley 94.The induction electrode 104 is connected to the high-voltage electrode18 and thus is kept at the same voltage existing thereon.

The pulley 95 is connected to the induction electrode 85 and ispositioned to engage the pellets, shortly after they leave the wheel 34.If the highvoltage electrode 18 is positively charged, the pellets atthis point are negatively charged, so that the pulley 95 and theinduction electrode 85 are charged with a voltage which is less positivethan that on the high-voltage electrode 18. Still another inductionelectrode 105 is disposed opposite the pulley 95 and is connected to thehighvoltage electrode 18 so as to be maintained at the voltage thereof.

The idler pulleys 93, 94 and 95 may all be of the same construction.They may be made of metal so as to be totally conductive, but it ispreferred to provide each pulley with a peripheral or rim portion 103(FIGS. 11 and 12) made of nylon or other suitable plastic material, toafiord the advantages of quiet operation and extremely long life. Theplastic material is electrically nonconductive, but contact is made withthe pellets 38 by means of one or more spring contactors 110. The springcontactors 110 could be of the same construction as employed on the mainpulleys or wheels 32 and 34. However, as shown in FIGS. 11 and 12, eachcontactor l is in the form of a plunger or pin biased outwardly by acoil spring 112. The contactor 110 and the spring 112 are mounted in atubular housing 114 which extends through an opening 116 in the plasticrim portion 108. Each of the pulleys 93-95 has a central portion 118which is also engaged by the housing 114. The central portion 118 andthe housing 114 are preferably made of metal or other electricallyconductive material. In this way, the contactor 110 is connected to thecentral portion 118 of the pulley and thence to the shaft 120 on whichthe pulley is mounted.

The plastic rim portion 108 is suitably secured to the central portion118, as by means of clamping plates 122 and 124, for example. Screws 126may be employed to secure the plates 122 and 124 to the central portion118 and the plastic rim portion 108.

A peripheral groove 128 is preferably provided in the plastic rimportion 108 to receive and retain the pellets 38 of the conveyor 30. Thecontactor 110 projects into the groove 128 so as to be engageable withthe pellets 38.

To improve the traction between the conveyor 30 and the idler pulleys93-95, it is preferred to provide the rim portion 108 of each pulleywith a plurality of angularly spaced teeth or ribs 130, projecting intothe peripheral groove 128. The teeth 13 are spaced so as to be readilyreceivable in the spaces between the pellets 38 on the conveyor 30.

All of the various induction electrodes 82-85 and 103-105 may be ofsubstantially the same construction. As shown to best advantage in FIGS.11 and 12, each induction electrode may be fonned with a U-shapedchannel 132, wider than the pellets 38 and adapted to embrace the rimportions of the various pulleys 32, 34, 93, 94 and 95, with ampleclearance between the induction electrodes and the pulleys. The U-shaped channel 132 has a cylindrically curved bottom portion 134 adaptedto be positioned opposite the pellets 38 of the conveyor 30.

In operation, the conveyor 30 carries electrostatic charges in bothdirections between the wheels 32 and 34, on the grounded frame 16 andthe high-voltage electrode 18. The conductive pellets 38 of the conveyor30 are charged by the voltage on the induction electrode 82, as thepellets depart from the wheel 32. If the voltage on the electrode 82 isnegative, the charges on the pellets will be positive, and vice versa.

The charges on the outbound pellets are coupled to the inductionelectrode 83 by the idler pulley 93, so that the electrode83 ismaintained at an operating voltage which is opposite in polarity to thevoltage impressed on the induction electrode 82 by the power supply 88.The induction electrode 83 prevents sparking between the returningpellets and the wheel 32.

The charged outbound pellets are conveyed across the high voltage whichexists between the high-voltage electrode 18 and the grounded frame 16,and are discharged to the highvoltage electrode through the wheel 34.The induction electrode prevents sparking between the incoming pelletsand the wheel 34.

The returning pellets are given charges of opposite sign high-voltagedepart from the wheel 34. These charges are induced by the electrode 84which derives its operating voltage from the idler pulley 94. Thecharges on the incoming pellets are conducted to the pulley 94 and theelectrode 84 until these elements are at the same voltage as thepellets, which is higher than the voltage on the high-voltage electrode18.

The operating voltage for the induction electrode 85 is derived from thereturning pellets by way of the idler pulley 95.

The charges on the returning pellets are transferred to ground by thewheel 32. The charges on the returning pellets are opposite in polarityto the charges on the outbound pellets.

The resilient contactors 70 on the main wheels 32 and 34 insure that thepellets 38 are conductively connected to the wheels, and thence to thegrounded frame 16 and the highvoltage electrode 18. Similarly, theresilient contactors on the idler pulleys 93-95 insure the electricalconnections will be established between the pellets and the idlerpulleys.

The charging of the pellets 38 is brought about by the energization ofthe power supply 88, so as to apply a high-voltage to the inductionelectrode 82. When the applied voltage is negative, the voltagedeveloped on the high-voltage electrode 18 will be positive and viceversa. For the case in which the voltage developed on the high-voltageelectrode or dome 18 is" positive, the voltage relationships are asfollows:

The voltage on the induction electrode 82 is stabilized and maintainedby the power supply 88. The voltages on the other main inductionelectrodes 83, 84 and 85 will be held accurately at the desiredpotentials by charge transfer to or from the pellets 38, only if theseadditional induction electrodes con form in shape and positioning,relative to the respective pulleys 32 and 34, so that the combination ofeach induction electrode and the corresponding pulley iselectrostatically equivalent to the combination of the inductionelectrode 82 and the pulley 32.

The charging rate is determined by the potential applied to theinduction electrode 82 by the power supply 88. During normal operation,the charge on each of the pulleys 93, 94 and 95 is substantiallyconstant, so that there is no appreciable flow of charge. It is onlywhen the charging rate is being changed that there is an appreciableflow of charges to the pulleys 93, 94 and 95. This flow persists onlylong enough to change the potentials on the induction electrodes 83, 84and 85 relative to the corresponding pulleys, so that these potentialsare kept equal in magnitude to the applied potential on the inductionelectrode 82, but with the appropriate sign.

The induction electrode arrangement achieves two important advantages.First, the returning pellets, on the downcoming run of the pellet chain,are given charges equal in mag nitude but opposite in sign to thecharges on the outgoing pellets. Thus, the total charging current ismaximized, yet is readily subject to control by the operator. Second,the arrangement of the induction electrodes brings about the transfer ofcharges between the pellets 38 and the pulleys 32 and 34 withoutsparking.

The action of the induction electrode 82 may be taken as an example.Each pellet 38 is in contact with the pulley 32 as the pellet moves intothe U-shaped opening of the induction electrode. The negative potentialon the induction electrode 82 causes a positive charge to flow to thepellet. As the pellet moves more deeply into the induction electrode, agreater positive charge is induced upon its surface. This charge flowsto the pellet without sparking, because the contact between the pelletand the pulley is maintained. The pellet moves to its maximum depthwithin the induction electrode before the pellet breaks contact with thepulley. As the pellet is leaving the pulley, constant depth ismaintained, so that the induced charge on the pellet is maintainedconstant. Thus, the current flow to the pellet drops to zero just beforethe contact break. Accordingly, there is no sparking between the pelletand the pulley. By the time the pellet is leaving the inductionelectrode 82, the pellet is far from the pulley, so that the charge canno longer escape.

The positive charge remains on each pellet 38 as it passes upwardly intothe high-voltage electrode or dome 18. There is no charge transfer whenthe pellet touches the pulley 94 because the charge is bound on thepellet by the induction electrode 104. The pellet now enters theinduction electrode 85 which also binds thepositive charge on thepellet. At the moment of contact with the pulley 34, there is no currentflow, because of this charge binding action of the induction electrode85. The charge flows from the pellet 38 to the pulley 34 as the pelletis leaving the influence of the induction electrode 85. The charge flowssmoothly while the pellet is in contact with the pulley 34. Thus, thereis no sparking and no energy loss.

The details of the charge transfer as each pellet 38 leaves the pulley34 are the same as previously described, except for the sign of thecharges, which are negative rather than positive. When the returningpellets arrive at the grounded pulley 32, the charge transfer is againaccomplished without sparking, in the same manner as when the pelletsarrive at the pulley 34.

To prevent sparking, all of the induction electrodes 82-85 should beidentical in shape and should be positioned identically with respect tothe pellet chain and the main pulleys 32 and 34. The electrostatic fieldconditions around the various induction electrodes should be closelymatched, so that different field conditions will not penetrate withinthe induction electrodes to any appreciable extent. If the inductionelectrodes are properly matched, the bound charge on each pellet at theinstant of contact or contact break with each pulley will be the same inall four cases.

Under normal operating conditions, the charge on each of the pulleys 93,94 and 95 is maintained constant so that there is no appreciable currentflow and no sparking. It is only when the charging rate is being changedthat there is any appreciable charge transfer to or from the pulleys,and even this current is transitory and of small magnitude.

The elimination of sparking under steady state conditions obviates thedust and corrosion problems that are associated with sparking. Moreover,the elimination of sparking obviates the energy loss that is associatedwith sparking. Accordingly, the charging system is highly efficient.

The pellet conveyor 30 can be operated at extremely high speeds, so thatthe charge carrying capacity of the conveyor will be high. The conveyoroperates quietly and efficiently. The conductive pellets 38 are freelyarticulated on the insulating links 40 so that the conveyor has a highdegree of flexibility.

Sparking does not normally occur along the conveyor 30, but anyaccidental sparking between the pellets 38 will not damage the conveyorin any way. Even a full scale flashover along the conveyor will notdamage the pellets 38 or the insulating links 40. Thus, the machine canbe kept in normal operation after any such flashover.

It will be evident that the high-voltage electrostatic generator of thepresent invention is capable of developing and maintaining a highervoltage, even with a higher load current than heretofore. The machineruns quietly even at extremely high speeds. If a flashover should occuralong the conveyor, no damage will occur to the conveyor. Thus, therewill be no need to shut down the machine for repairs.

Various other modifications, alternative constructions and equivalentsmay be employed, as will be understood by those skilled in the art.

We claim:

1. A charge-carrying conveyor for a high-voltage electrostaticgenerator,

comprising an endless chain having electrically conductive linksalternating with electrically insulating links,

said electrically conductive links being generally cylindrical andhaving cylindrical openings extending axially therein, said electricallyinsulating links being swingably received in said cylindrical openings,

and means forming pivot connections between the successive electricallyconductive and electrically insulating links.

2. A charge-carrying conveyor according to claim 1,

in which each of said electrically conductive links has a generallycylindrical exterior portion.

3. A charge-carrying conveyor according to claim 2,

in which said generally cylindrical exterior portion is formed with acircumferential groove.

4. A charge-carrying conveyor according to claim 1,

in which said last-mentioned means comprise pivot pin elements extendingbetween said electrically conductive and electrically insulating links.

5. A charge-carrying conveyor according to claim 4,

in which said pivot pin elements comprise pivot pins extending throughopenings in said links.

6. A charge-carrying conveyor according to claim 1,

in which each of said electrically insulating links is formed withenlarged end portions received in said cylindrical openings for rockingmovement.

7. A charge-carrying conveyor according to claim 6,

in which each of said electrically insulating links has a reducedmidportion between said enlarged end portions.

8. A charge-carrying conveyor according to claim 1,

in which each of said electrically insulating links is formed withrounded end portions rockably received in said cylindrical openings.

9. A charge-carrying conveyor according to claim 8,

in which said rounded end portions are spherically curved.

10. A charge-carrying conveyor according to claim 1,

in which each of said electrically insulating links is formed withenlarged spherically rounded end portions rockably received in saidcylindrical openings.

1 l. A charge-carrying conveyor according to claim 1,

in which said last-mentioned means comprise two pivot elements extendingbetween said electrically insulating and electrically conductive links,

said electrically insulating links having enlarged spherically roundedend portions received in said cylindrical openings,

said pivot elements extending between said enlarged end portions andsaid electrically conductive links. 12. In a high-voltage electrostaticgenerator, the combination comprising an endless charge-carryingconveyor including electrically conductive pellets with electricallyinsulating elements therebetween,

a wheel having an edge portion with a circumferential groove forreceiving and guiding said endless conveyor,

and at least one contactor mounted on said wheel and projecting intosaid groove for electrically contacting said conductive pellets.

13. A combination according to claim 12, in which said edge portion ismade of electrically insulating material.

14. A combination according to claim 12, in which said contactor isprovided with resilient mounting means between said contactor and saidwheel whereby spring pressure is applied between said contactor and thecorresponding conductive pellets.

l5. A combination according to claim 12, including a plurality of suchcontactors mounted on said wheel and projecting into said groove forelectrically contacting said pellets.

16. A combination according to claim 12, in which said contactorcomprises a flexible conductive spring mounted on said wheel.

17. A combination according to claim 15,

in which said contractors comprise flexible conductive springs mountedon said wheel and spaced around the periphery thereof.

18. A combination according to claim 12,

in which said contactor comprises a radially movable plunger,

and a spring biasing said plunger into said groove.

19. In a high-voltage electrostatic generator,

the combination comprising an endless charge-carrying conveyor includinga plurality of electrically conductive pellets with electricallyinsulating elements disposedtherebetween,

a pair of wheel for supporting and circulating said conveyor,

and a charging system including at least one pulley having means thereonfor electrically contacting said pellets, said endless conveyor having alongitudinal axis,

said pellets having substantially larger radial dimensions from saidaxis than the radial dimensions of said insulating elements,

said pellets being engageable with said pulley for holding saidinsulating elements away from said pulley to provide gaps between saidpulley and said insulating elements.

20. A combination according to claim 19,

in which said last-mentioned means include an electrically conductiveportion of said pulley.

21. A combination according to claim 19,

in which said last-mentioned means comprise a contactor mounted on saidpulley for contacting said pellets.

22. In a high-voltage electrostatic generator,

the combination comprising an endless charge-carrying conveyor includinga plurality of electrically conductive pellets with electricallyinsulating elements disposed therebetween,

a pair of wheels for supporting and circulating said conveyor,

and a charging system including at least one pulley having means thereonfor electrically contacting said pellets,

said pulley including an electrically insulating rim portion forengaging and guiding said conveyor,

said last-mentioned means including a conductive contactor mounted onsaid pulley and projecting from said insulatin rim portion to engagesaid pellets.

23. g combination according to claim 19, including an inductionelectrode disposed opposite said pulley in a position such that saidpellets are influenced by said electrode when said pellets are engagingsaid pulley.

24. A combination according to claim 23,

in which said induction electrode is shaped to provide a channel throughwhich said pellets are caused to travel when said pellets are engagingsaid pulley.

22;;33 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3'6l2'9l9 Dated October 12, I971 Immntor) Raymond G. Herb and James A.Ferry It is certified that error appears in the above-identified patentand that said Letters Pat ent are hereby corrected as shown below:

Column 5, line 72, "13" should be -l30-.

column .6, line 31, "high voltage" should be --as they-.

Signed and sealed this lL th day of March 1972.

(SEAL) At-test:

EDWARD M.FLETCHER,JR.

ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents.

1. A charge-carrying conveyor for a high-voltage electrostaticgenerator, comprising an endless chain having electrically conductivelinks alternating with electrically insulating links, said electricallyconductive links being generally cylindrical and having cylindricalopenings extending axially therein, said electrically insulating linksbeing swingably received in said cylindrical openings, and means formingpivot connections between the successive electrically conductive andelectrically insulating links.
 2. A charge-carrying conveyor accordingto claim 1, in which each of said electrically conductive links has agenerally cylindrical exterior portion.
 3. A charge-carrying conveyoraccording to claim 2, in which said generally cylindrical exteriorportion is formed with a circumferential groove.
 4. A charge-carryingconveyor according to claim 1, in which said last-mentioned meanscomprise pivot pin elements extending between said electricallyconductive and electrically insulating links.
 5. A charge-carryingconveyor according to claim 4, in which said pivot pin elements comprisepivot pins extending through openings in said links.
 6. Acharge-carrying conveyor according to claim 1, in which each of saidelectrically insulating links is formed with enlarged end portionsreceived in said cylindrical openings for rocking movement.
 7. Acharge-carrying conveyor according to claim 6, in which each of saidelectrically insulating links has a reduced midportion between saidenlarged end portions.
 8. A charge-carrying conveyor according to claim1, in which each of said electrically insulating links is formed withrounded end portions rockably received in said cylindrical openings. 9.A charge-carrying conveyor according to claim 8, in which said roundedend portions are spherically curved.
 10. A charge-carrying conveyoraccording to claim 1, in which each of said electrically insulatinglinks is formed with enlarged spherically rounded end portions rockablyreceived in said cylindrical openings.
 11. A charge-carrying conveyoraccording to claim 1, in which said last-mentioned means comprise twopivot elements extending between said electrically insulating andelectrically conductive links, said electrically insulating links havingenlarged spherically rounded end portions received in said cylindricalopenings, said pivot elements extending between said enlarged endportions and said electrically conductive links.
 12. In a high-voltageelectrostatic generator, the combination comprising an endlesscharge-carrying conveyor including electrically conductive pellets withelectrically insulating elements therebetween, a wheel having an edgeportion with a circumferential groove for receiving and guiding saidendless conveyor, and at least one contactor mounted on said wheel andprojecting into said groove for electrically contacting said conductivepellets.
 13. A combination according to claim 12, in which said edgeportion is made of electrically insulating material.
 14. A combinationaccording to claim 12, in which said contactor is provided withresilient mounting means between said contactor and said wheel wherebyspring pressure is applied between said contactor and the correspoNdingconductive pellets.
 15. A combination according to claim 12, including aplurality of such contactors mounted on said wheel and projecting intosaid groove for electrically contacting said pellets.
 16. A combinationaccording to claim 12, in which said contactor comprises a flexibleconductive spring mounted on said wheel.
 17. A combination according toclaim 15, in which said contractors comprise flexible conductive springsmounted on said wheel and spaced around the periphery thereof.
 18. Acombination according to claim 12, in which said contactor comprises aradially movable plunger, and a spring biasing said plunger into saidgroove.
 19. In a high-voltage electrostatic generator, the combinationcomprising an endless charge-carrying conveyor including a plurality ofelectrically conductive pellets with electrically insulating elementsdisposed therebetween, a pair of wheel for supporting and circulatingsaid conveyor, and a charging system including at least one pulleyhaving means thereon for electrically contacting said pellets, saidendless conveyor having a longitudinal axis, said pellets havingsubstantially larger radial dimensions from said axis than the radialdimensions of said insulating elements, said pellets being engageablewith said pulley for holding said insulating elements away from saidpulley to provide gaps between said pulley and said insulating elements.20. A combination according to claim 19, in which said last-mentionedmeans include an electrically conductive portion of said pulley.
 21. Acombination according to claim 19, in which said last-mentioned meanscomprise a contactor mounted on said pulley for contacting said pellets.22. In a high-voltage electrostatic generator, the combinationcomprising an endless charge-carrying conveyor including a plurality ofelectrically conductive pellets with electrically insulating elementsdisposed therebetween, a pair of wheels for supporting and circulatingsaid conveyor, and a charging system including at least one pulleyhaving means thereon for electrically contacting said pellets, saidpulley including an electrically insulating rim portion for engaging andguiding said conveyor, said last-mentioned means including a conductivecontactor mounted on said pulley and projecting from said insulating rimportion to engage said pellets.
 23. A combination according to claim 19,including an induction electrode disposed opposite said pulley in aposition such that said pellets are influenced by said electrode whensaid pellets are engaging said pulley.
 24. A combination according toclaim 23, in which said induction electrode is shaped to provide achannel through which said pellets are caused to travel when saidpellets are engaging said pulley.